In the manufacture of a three-dimensional stacked semiconductor memory such as a 3D NAND flash memory, a process of etching a multilayered film in a step shape by using plasma is performed. In the process of etching the multilayered film in the step shape, etching of the multilayered film having a mask formed on a surface thereof and trimming of the mask on the multilayered film are alternately performed. To form the step shape by using a stacked structure of the multilayered film, it is important in the trimming of the mask to increase an etching rate of a mask material in the horizontal direction with respect to an etching rate in the vertical direction.
Patent Document 1: International Publication No. WO 2013/121936
In the prior art etching of the step shape, however, roughness of an end surface portion of the step shape is increased.